U.S. patent application number 15/070607 was filed with the patent office on 2016-08-04 for work function-controlled carbon nanomaterial and metal nanowire hybrid transparent conductive film and method for manufacturing same.
This patent application is currently assigned to KOREA ELECTROTECHNOLOGY RESEARCH INSTITUTE. The applicant listed for this patent is KOREA ELECTROTECHNOLOGY RESEARCH INSTITUTE. Invention is credited to Kang-jun Baeg, Joong-tark Han, Hee-jin Jeong, Seung-yol Jeong, Geon-woong Lee, Jong-seuk Woo.
Application Number | 20160222227 15/070607 |
Document ID | / |
Family ID | 54288080 |
Filed Date | 2016-08-04 |
United States Patent
Application |
20160222227 |
Kind Code |
A1 |
Han; Joong-tark ; et
al. |
August 4, 2016 |
WORK FUNCTION-CONTROLLED CARBON NANOMATERIAL AND METAL NANOWIRE
HYBRID TRANSPARENT CONDUCTIVE FILM AND METHOD FOR MANUFACTURING
SAME
Abstract
Disclosed is a method of manufacturing a work
function-controlled carbon nanomaterial and metal nanowire hybrid
transparent conductive film, including: a first step of modifying
the surface of a carbon nanomaterial to introduce a functional
group to a conductive carbon nanomaterial; a second step of forming
a work function-reduced carbon nanomaterial dispersed solution by
mixing and reacting the carbon nanomaterial, which is
functionalized in the first step, with an isocyanate-based compound
and a pyrimidine-based compound; a third step of forming a
single-component coating solution by hybridizing the work
function-reduced carbon nanomaterial dispersed solution obtained in
the second step with a metal nanowire; and a fourth step of forming
a film by applying the coating solution, which is formed in the
third step, on a substrate.
Inventors: |
Han; Joong-tark;
(Changwon-si, KR) ; Lee; Geon-woong; (Changwon-si,
KR) ; Baeg; Kang-jun; (Changwon-si, KR) ; Woo;
Jong-seuk; (Daegu, KR) ; Jeong; Seung-yol;
(Gimhae-si, KR) ; Jeong; Hee-jin; (Changwon-si,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KOREA ELECTROTECHNOLOGY RESEARCH INSTITUTE |
Changwon-si |
|
KR |
|
|
Assignee: |
KOREA ELECTROTECHNOLOGY RESEARCH
INSTITUTE
|
Family ID: |
54288080 |
Appl. No.: |
15/070607 |
Filed: |
March 15, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/KR2015/003440 |
Apr 7, 2015 |
|
|
|
15070607 |
|
|
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01B 5/14 20130101; C09D
5/24 20130101; C01B 32/15 20170801; H01B 1/04 20130101; C01B 32/194
20170801; H01B 1/02 20130101; C01B 32/168 20170801; C01B 32/174
20170801; B05D 5/12 20130101 |
International
Class: |
C09D 5/24 20060101
C09D005/24 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 7, 2014 |
KR |
10-2014-0041369 |
Claims
1. A method of manufacturing a work function-controlled carbon
nanomaterial and metal nanowire hybrid transparent conductive film,
comprising: a first step of modifying a surface of a carbon
nanomaterial to introduce a functional group to a conductive carbon
nanomaterial; a second step of forming a work function-reduced
carbon nanomaterial dispersed solution by mixing and reacting the
carbon nanomaterial, which is functionalized in the first step,
with an isocyanate-based compound and a pyrimidine-based compound;
a third step of forming a single-component coating solution by
hybridizing the work function-reduced carbon nanomaterial dispersed
solution obtained in the second step with a metal nanowire; and a
fourth step of forming a film by applying the coating solution,
which is formed in the third step, on a substrate.
2. The method of claim 1, wherein the carbon nanomaterial comprises
at least one selected from the group consisting of single-walled
carbon nanotubes, double-walled carbon nanotubes, multi-walled
carbon nanotubes, and graphene.
3. The method of claim 1, wherein the metal nanowire comprises at
least one selected from the group consisting of a silver nanowire
and a copper nanowire.
4. The method of claim 1, wherein the isocyanate-based compound
comprises at least one selected from the group consisting of
ethylene diisocyanate, 1,4-tetramethylene diisocyanate,
1,6-hexamethylene diisocyanate (HDI), 1,12-dodecane diisocyanate,
cyclobutane-1,3-diisocyanate, cyclohexane-1,3-diisocyanate,
cyclohexane-1,4-diisocyanate,
1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane,
2,4-hexahydrotoluene diisocyanate, 2,6-hexahydrotoluene
diisocyanate, hexahydro-1,3-phenylene diisocyanate,
hexahydro-1,4-phenylene diisocyanate, perhydro-2,4'-d
iphenylmethane diisocyanate, perhydro-4,4'-diphenylmethane
diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene
diisocyanate, 1,4-durol diisocyanate (DDI), 4,4'-stilbene
diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate (TODI),
toluene 2,4-diisocyanate, toluene 2,6-diisocyanate (TDI),
diphenylmethane-2,4'-diisocyanate (MDI), 2,2'-diphenylmethane
diisocyanate (MDI), diphenylmethane-4,4'-diisocyanate (MDI),
naphthalene-1,5-isocyanate (NDI), 2,2'-methylenediphenyl
diisocyanate, 5,7-diisocyanatonaphthalene-1,4-dione, isophorone
diisocyanate, m-xylene diisocyanate,
3,3'-dimethoxy-4,4'-biphenylene diisocyanate,
3,3'-dimehtoxybenzidine-4,4'-diisocyanate, toluene 2,4-diisocyanate
terminal-having poly(propylene glycol), toluene 2,4-diisocyanate
terminal-having poly(ethylene glycol), triphenylmethane
triisocyanate, diphenylmethane triisocyanate,
butane-1,2,2'-triisocyanate, trimethylolpropane tolylene
diisocyanate trimer, 2,4,4'-diphenyl ether triisocyanate,
isocyanurate having a plurality of hexamethylene diisocyanates,
iminooxadiazine having a plurality of hexamethylene diisocyanates,
and polymethylene polyphenyl isocyanate.
5. The method of claim 1, wherein the pyrimidine-based compound
comprises at least one selected from the group consisting of
2-amino-6-methyl-1H-pyrido[2,3-d]pyrimidin-4-one,
2-amino-6-bromopyrido[2,3-d]pyridin-4(3H)-one,
2-amino-4-hydroxy-5-pyrimidine carboxylic acid ethyl ester,
2-amino-6-ethyl-4-hydroxypyrimidine, 2-amino-4-hydroxy-6-methyl
pyrimidine, and 2-amino-5,6-dimethyl-4-hydroxypyrimidine.
6. The method of claim 1, wherein the work function of the carbon
nanomaterial is reduced by 0.1 eV or more.
7. A work function-controlled carbon nanomaterial and metal
nanowire hybrid transparent conductive film, formed by mixing and
reacting a carbon nanomaterial having a functional group introduced
through acid treatment with an isocyanate-based compound and a
pyrimidine-based compound to obtain a work function-reduced carbon
nanomaterial dispersed solution, hybridizing the dispersed solution
with a metal nanowire, thus preparing a single-component coating
solution, and applying the coating solution on a substrate.
8. The hybrid transparent conductive film of claim 7, wherein the
carbon nanomaterial comprises at least one selected from the group
consisting of single-walled carbon nanotubes, double-walled carbon
nanotubes, multi-walled carbon nanotubes, and graphene.
9. The hybrid transparent conductive film of claim 7, wherein the
metal nanowire comprises at least one selected from the group
consisting of a silver nanowire and a copper nanowire.
10. The hybrid transparent conductive film of claim 7, wherein the
isocyanate-based compound comprises at least one selected from the
group consisting of ethylene diisocyanate, 1,4-tetramethylene
diisocyanate, 1,6-hexamethylene diisocyanate (HDI), 1,12-dodecane
diisocyanate, cyclobutane-1,3-diisocyanate,
cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate,
1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane,
2,4-hexahydrotoluene diisocyanate, 2,6-hexahydrotoluene
diisocyanate, hexahydro-1,3-phenylene diisocyanate,
hexahydro-1,4-phenylene diisocyanate, perhydro-2,4'-diphenylmethane
diisocyanate, perhydro-4,4'-diphenylmethane diisocyanate,
1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 1,4-durol
diisocyanate (DDI), 4,4'-stilbene diisocyanate,
3,3'-dimethyl-4,4'-biphenylene diisocyanate (TODI), toluene
2,4-diisocyanate, toluene 2,6-diisocyanate (TDI),
diphenylmethane-2,4'-diisocyanate (MDI), 2,2'-diphenylmethane
diisocyanate (MDI), diphenylmethane-4,4'-diisocyanate (MDI),
naphthalene-1,5-isocyanate (NDI), 2,2'-methylenediphenyl
diisocyanate, 5,7-diisocyanatonaphthalene-1,4-dione, isophorone
diisocyanate, m-xylene diisocyanate,
3,3'-dimethoxy-4,4'-biphenylene diisocyanate,
3,3'-dimehtoxybenzidine-4,4'-diisocyanate, toluene 2,4-diisocyanate
terminal-having poly(propylene glycol), toluene 2,4-diisocyanate
terminal-having poly(ethylene glycol), triphenylmethane
triisocyanate, diphenylmethane triisocyanate,
butane-1,2,2'-triisocyanate, trimethylolpropane tolylene
diisocyanate trimer, 2,4,4'-diphenyl ether triisocyanate,
isocyanurate having a plurality of hexamethylene diisocyanates,
iminooxadiazine having a plurality of hexamethylene diisocyanates,
and polymethylene polyphenyl isocyanate.
11. The hybrid transparent conductive film of claim 7, wherein the
pyrimidine-based compound comprises at least one selected from the
group consisting of
2-amino-6-methyl-1H-pyrido[2,3-d]pyrimidin-4-one,
2-amino-6-bromopyrido[2,3-d]pyridin-4(3H)-one,
2-amino-4-hydroxy-5-pyrimidine carboxylic acid ethyl ester,
2-amino-6-ethyl-4-hydroxypyrimidine, 2-amino-4-hydroxy-6-methyl
pyrimidine, and 2-amino-5,6-dimethyl-4-hydroxypyrimidine.
12. The hybrid transparent conductive film of claim 7, wherein the
work function of the carbon nanomaterial is reduced by 0.1 eV or
more.
Description
REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation of pending International Patent
Application PCT/KR2015/003440 filed on Apr. 7, 2015 which
designates the United States and claims priority of Korean Patent
Application No. 10-2014-0041369 filed on Apr. 7, 2014, the entire
contents of which are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a work function-controlled
carbon nanomaterial and metal nanowire hybrid transparent
conductive film and a method of manufacturing the same and, more
particularly, to a work function-controlled carbon nanomaterial and
metal nanowire hybrid transparent conductive film and a method of
manufacturing the same, wherein a conductive carbon nanomaterial,
such as carbon nanotubes, graphene, etc., is mixed and reacted with
an isocyanate-based compound and a pyrimidine-based compound, thus
forming a carbon nanomaterial, the work function of which is
controlled and which is dispersed without the use of a dispersant,
followed by hybridizing the carbon nanomaterial with a metal
nanowire having high conductivity, such as a silver nanowire or a
copper nanowire, to give a single-component coating solution, which
is then used to manufacture a film configured such that a network
is formed between the metal nanowire and the carbon nanomaterial,
thereby ensuring electrical stability through work function
matching of the metal nanowire and solving optical problems such as
haze.
BACKGROUND OF THE INVENTION
[0003] Typically, a transparent conductive film is used for a
plasma display panel (PDP), a liquid crystal display (LCD) device,
a light-emitting diode (LED), an organic electroluminescent device
(OLED), a touch panel, a solar cell, a transparent heater, etc.
[0004] Such a transparent conductive film, having high conductivity
(e.g. a sheet resistance of 1.times.10.sup.3 .OMEGA./sq or less)
and high transmittance in the visible light range, is being
utilized for electrodes in a variety of light-receiving and
light-emitting devices, as well as solar cells, liquid crystal
display devices, plasma display panels, and smart windows, and
additional applications thereof include transparent electromagnetic
wave-shielding members such as antistatic films and electromagnetic
shielding films for windows for vehicles or buildings, and
transparent heat-generating members such as solar reflective films,
glass showcases, etc.
[0005] Examples of the transparent conductive film include a tin
oxide (SnO.sub.2) film doped with antimony or fluorine, a zinc
oxide (ZnO) film doped with aluminum or potassium, and a tin-doped
indium oxide (In.sub.2O.sub.3) film.
[0006] In particular, a tin-doped indium oxide film, namely an
In.sub.2O.sub.3--Sn film, which is referred to as an ITO (Indium
tin oxide) film, is most commonly used because a low-resistance
film may be readily acquired. Although ITO is superior in various
properties and is mainly applied to processes, indium oxide
(In.sub.2O.sub.3) is produced as a byproduct from zinc (Zn) mines,
and thus the demand therefor and supply thereof are not balanced.
Furthermore, an ITO film is not flexible and thus cannot be
employed in flexible materials such as polymer substrates, and the
production cost thereof is increased because of the manufacture
under high-temperature and high-pressure conditions.
[0007] Also, the upper surface of a polymer substrate may be coated
with a conductive polymer to obtain a flexible display, but the
formed film may deteriorate electrical conductivity when exposed to
the exterior environment, or may not be transparent, and the use
thereof is limited.
[0008] With the goal of solving such problems, actively being
studied are methods in which various kinds of substrates are coated
with carbon nanotubes or metal nanowires as a one-dimensional
structure, or alternatively, graphene, having a two-dimensional
structure, may be synthesized using chemical vapor deposition and
may then be transferred to the substrate. When the carbon nanotubes
are provided in the form of a network-type transparent conductive
film, junction resistance is very high, making it difficult to
drastically lower sheet resistance. In the case where
semiconductive carbon nanotubes are contained, they suffer in that
they are sensitive to the external environment.
[0009] As for metal nanowires, the resistance of nanowires alone is
very low and thus, even when they are provided in the form of a
network-type transparent conductive film, sheet resistance is
remarkably decreased compared to the case of carbon nanotubes.
However, in the case where the diameter of the metal nanowires is
decreased and the resistance occurring at a junction of the network
is high, the junction may be undesirably melted and broken due to
electrical influence. Furthermore, the metal nanowires may cause
problems of haze and light reflection when applied to displays.
Also, when they are applied to multilayered optoelectronic devices,
superior characteristics are exhibited, as long as contact problems
of upper and lower materials and work function matching problems
are solved.
[0010] Therefore, in order to apply the metal nanowires to
displays, touch panels, various optical devices, transparent
heaters, etc., metal nanowire-based transparent conductive films
having ensured electrical, optical and mechanical stabilities have
to be provided. To this end, there is a need for a single-component
carbon nanomaterial and metal nanowire hybrid transparent
conductive film in which work function matching problems are solved
and which has good dispersibility, even without the use of a
dispersant.
SUMMARY OF THE INVENTION
[0011] Accordingly, the present invention has been made keeping in
mind the above problems encountered in the related art, and an
object of the present invention is to provide a work
function-controlled carbon nanomaterial and metal nanowire hybrid
transparent conductive film and a method of manufacturing the same,
wherein a conductive carbon nanomaterial, such as carbon nanotubes,
graphene, etc., is mixed and reacted with an isocyanate-based
compound and a pyrimidine-based compound, thus forming a carbon
nanomaterial, the work function of which is controlled and which is
dispersed without the use of a dispersant, followed by hybridizing
the carbon nanomaterial with a metal nanowire having high
conductivity, such as a silver nanowire or a copper nanowire, to
give a single-component coating solution, which is then used to
manufacture a film configured such that a network is formed between
the metal nanowire and the carbon nanomaterial, thereby ensuring
electrical stability through work function matching of the metal
nanowire and solving optical problems such as haze.
[0012] In order to accomplish the above object, the present
invention provides a method of manufacturing a work
function-controlled carbon nanomaterial and metal nanowire hybrid
transparent conductive film, comprising: a first step of modifying
a surface of a carbon nanomaterial to introduce a functional group
to a conductive carbon nanomaterial; a second step of forming a
work function-reduced carbon nanomaterial dispersed solution by
mixing and reacting the carbon nanomaterial, which is
functionalized in the first step, with an isocyanate-based compound
and a pyrimidine-based compound; a third step of forming a
single-component coating solution by hybridizing the work
function-reduced carbon nanomaterial dispersed solution obtained in
the second step with a metal nanowire; and a fourth step of forming
a film by applying the coating solution, which is formed in the
third step, on a substrate.
[0013] In addition, the present invention provides a work
function-controlled carbon nanomaterial and metal nanowire hybrid
transparent conductive film, formed by mixing and reacting a carbon
nanomaterial having a functional group introduced through acid
treatment with an isocyanate-based compound and a pyrimidine-based
compound to obtain a work function-reduced carbon nanomaterial
dispersed solution, hybridizing the dispersed solution with a metal
nanowire, thus preparing a single-component coating solution, and
applying the coating solution on a substrate.
[0014] The carbon nanomaterial may include at least one selected
from the group consisting of single-walled carbon nanotubes,
double-walled carbon nanotubes, multi-walled carbon nanotubes, and
graphene.
[0015] The metal nanowire may include at least one selected from
the group consisting of a silver nanowire and a copper
nanowire.
[0016] The isocyanate-based compound may include at least one
selected from the group consisting of ethylene diisocyanate,
1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate
(HDI), 1,12-dodecane diisocyanate, cyclobutane-1,3-diisocyanate,
cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate,
1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane,
2,4-hexahydrotoluene diisocyanate, 2,6-hexahydrotoluene
diisocyanate, hexahydro-1,3-phenylene diisocyanate,
hexahydro-1,4-phenylene diisocyanate, perhydro-2,4'-diphenylmethane
diisocyanate, perhydro-4,4'-diphenylmethane diisocyanate,
1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 1,4-durol
diisocyanate (DDI), 4,4'-stilbene diisocyanate,
3,3'-dimethyl-4,4'-biphenylene diisocyanate (TODI), toluene
2,4-diisocyanate, toluene 2,6-diisocyanate (TDI),
diphenylmethane-2,4'-diisocyanate (MDI), 2,2'-diphenylmethane
diisocyanate (MDI), diphenylmethane-4,4'-diisocyanate (MDI),
naphthalene-1,5-isocyanate (NDI), 2,2'-methylenediphenyl
diisocyanate, 5,7-diisocyanatonaphthalene-1,4-dione, isophorone
diisocyanate, m-xylene diisocyanate,
3,3'-dimethoxy-4,4'-biphenylene diisocyanate,
3,3'-dimehtoxybenzidine-4,4'-diisocyanate, toluene 2,4-diisocyanate
terminal-having poly(propylene glycol), toluene 2,4-diisocyanate
terminal-having poly(ethylene glycol), triphenylmethane
triisocyanate, diphenylmethane triisocyanate,
butane-1,2,2'-triisocyanate, trimethylolpropane tolylene
diisocyanate trimer, 2,4,4'-diphenyl ether triisocyanate,
isocyanurate having a plurality of hexamethylene diisocyanates,
iminooxadiazine having a plurality of hexamethylene diisocyanates,
and polymethylene polyphenyl isocyanate.
[0017] The pyrimidine-based compound may include at least one
selected from the group consisting of
2-amino-6-methyl-1H-pyrido[2,3-d]pyrimidin-4-one,
2-amino-6-bromopyrido[2,3-d]pyridin-4(3H)-one,
2-amino-4-hydroxy-5-pyrimidine carboxylic acid ethyl ester,
2-amino-6-ethyl-4-hydroxypyrimidine, 2-amino-4-hydroxy-6-methyl
pyrimidine, and 2-amino-5,6-dimethyl-4-hydroxypyrimidine.
[0018] The work function of the carbon nanomaterial is preferably
reduced by 0.1 eV or more.
[0019] Accordingly, in the manufacture of a transparent conductive
film having a network structure configured such that a work
function-controlled carbon nanomaterial and a metal nanowire are
hybridized, because a carbon nanomaterial having a work function
similar to that of the metal nanowire is used, when voltage is
applied to the transparent conductive film, current is induced to
flow toward the junction between the metal nanowire and the carbon
nanomaterial, rather than toward the junction of the metal
nanowire, thus assuring the electrical stability of the transparent
conductive film. Moreover, the use of a carbon nanomaterial having
optically low haze and mechanical stability results in a
transparent conductive film in which the haze of the metal nanowire
network is lowered and mechanical stability is enhanced.
[0020] According to the present invention, a conductive carbon
nanomaterial, such as carbon nanotubes, graphene, etc., is mixed
and reacted with an isocyanate-based compound and a
pyrimidine-based compound, thus forming a carbon nanomaterial, the
work function of which is controlled and which is dispersed without
the use of a dispersant, followed by hybridizing the carbon
nanomaterial with a metal nanowire having high conductivity, such
as a silver nanowire or a copper nanowire, to give a
single-component coating solution, which is then used to
manufacture a film configured such that a network is formed between
the metal nanowire and the carbon nanomaterial, thereby ensuring
electrical stability through work function matching of the metal
nanowire and solving optical problems such as haze.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 illustrates the UV photoelectron spectroscopy
spectrum, which is analyzed in order to evaluate the work function
of a conductor used in the manufacture of a transparent conductive
film according to an embodiment of the present invention and a work
function measured thereby;
[0022] FIGS. 2A to 2D illustrate scanning electron microscope (SEM)
images of the silver nanowire/carbon nanotube hybrid transparent
conductive film for varying amounts of single-walled carbon
nanotubes according to an embodiment of the present invention;
[0023] FIGS. 3A to 3B illustrate changes in temperature when
voltage is applied to the silver nanowire-transparent conductive
film (FIG. 3A) of Comparative Example and the silver
nanowire/carbon nanotube hybrid transparent conductive film (FIG.
3B) of Example according to the present invention, and temperature
distribution images taken by an IR camera;
[0024] FIGS. 4A to 4B illustrate SEM images of the surfaces of the
silver nanowire-transparent conductive film (FIG. 4A) of
Comparative Example and the silver nanowire/carbon nanotube hybrid
transparent conductive film (FIG. 4B) of Example according to the
present invention, after the application of voltage of 10 V;
and
[0025] FIG. 5A schematically illustrates the band structure formed
in the junction of the silver nanowires and the carbon nanotubes,
in which, when the work function is decreased in the present
invention, a difference in work function from the silver nanowires
is lowered, and FIG. 5B schematically illustrates changes in
electricity flow path due to a reduction in the junction resistance
of the silver nanowires and the carbon nanotubes.
DETAILED DESCRIPTION OF THE INVENTION
[0026] Hereinafter, a detailed description will be given of
preferred embodiments of the present invention with reference to
the appended drawings.
[0027] FIG. 1 illustrates the UV photoelectron spectroscopy
spectrum, which is analyzed in order to evaluate the work function
of a conductor used in the manufacture of a transparent conductive
film according to an embodiment of the present invention and a work
function measured thereby, FIGS. 2A to 2D illustrate SEM images of
the silver nanowire/carbon nanotube hybrid transparent conductive
film for varying amounts of single-walled carbon nanotubes
according to an embodiment of the present invention, FIGS. 3A to 3B
illustrate changes in temperature when voltage is applied to the
silver nanowire-transparent conductive film (FIG. 3A) of
Comparative Example and the silver nanowire/carbon nanotube hybrid
transparent conductive film (FIG. 3B) of Example according to the
present invention, and temperature distribution images taken by an
IR camera, FIG. 4A to 4B illustrate SEM images of the surfaces of
the silver nanowire-transparent conductive film (FIG. 4A) of
Comparative Example and the silver nanowire/carbon nanotube hybrid
transparent conductive film (FIG. 4B) of Example according to the
present invention, after the application of voltage of 10 V, FIG.
5A schematically illustrates the band structure formed in the
junction of the silver nanowires and the carbon nanotubes, in
which, when the work function is decreased in the present
invention, a difference in work function from the silver nanowires
is lowered, and FIG. 5B schematically illustrates changes in
electricity flow path due to a reduction in the junction resistance
of the silver nanowires and the carbon nanotubes.
[0028] As illustrated in the drawings, the method of manufacturing
a work function-controlled carbon nanomaterial and metal nanowire
hybrid transparent conductive film according to the present
invention broadly comprises: a first step of modifying the surface
of a carbon nanomaterial, a second step of forming a work
function-reduced carbon nanomaterial dispersed solution, a third
step of forming a single-component coating solution by hybridizing
the carbon nanomaterial dispersed solution and metal nanowires, and
a fourth step of forming a film by applying the coating solution on
a substrate.
[0029] An embodiment of the present invention is directed to a
method of manufacturing a transparent conductive film configured
such that the carbon nanotubes and the metal nanowires are
hybridized using a coating solution obtained by mixing work
function-controlled single-walled carbon nanotubes with metal
nanowires. In the present embodiment, the work function of the
carbon nanotubes is lowered in a manner in which a functional group
containing a large number of nitrogen atoms is introduced.
[0030] The first step is described below.
[0031] Specifically, 10 g of single-walled carbon nanotubes are
mixed with 200 mL of a mixed solution comprising sulfuric acid and
nitric acid (7:3 volume ratio), and the resulting mixture is heated
to 80.degree. C., stirred for 24 hr, and then cooled to room
temperature.
[0032] Thereafter, the mixture is diluted with 800 mL of distilled
water.
[0033] The diluted solution is filtered four times or more with
filter paper so that the remaining acid solution is removed from
the carbon nanotubes, followed by a drying process, thereby
affording single-walled carbon nanotubes having a carboxyl
functional group (--COOH) introduced thereto.
[0034] In the next second step, the single-walled carbon nanotubes
having a carboxyl group (--COOH) are dispersed in an amount of
100/L in an N-methyl pyrrolidone solvent, mixed with toluene
diisocyanate as a diisocyanate compound, and reacted with stirring
at 100.degree. C. for 12 hr, whereby the isocyanate group is
introduced.
[0035] Subsequently, the carbon nanotubes having the isocyanate
group introduced thereto are mixed with
2-amino-4-hydroxy-6-methyl-pyrimidine and stirred at 100.degree. C.
for 20 hr so as to carry out a junction reaction, thereby injecting
electrons to the carbon nanotubes to thus introduce
2-ureido-4[1H]pyrimidinone containing a plurality of nitrogen
atoms, which are able to reduce the work function. This is deemed
to be because nitrogen atoms are electron-rich.
[0036] The work function of the single-walled carbon nanotubes is
measured using ultraviolet photoelectron spectroscopy. The results
are shown in FIG. 1.
[0037] In FIG. 1, the untreated carbon nanotubes are the carbon
nanotubes of Comparative Example after the first step and before
the second step, and the nitrogen-containing carbon nanotubes are
the work function-reduced carbon nanotubes after the first and
second steps. As illustrated in FIG. 1, the work function of the
nitrogen-containing carbon nanotubes according to the present
invention is decreased by 0.4 eV compared to the untreated
single-walled carbon nanotubes, thus reaching 4.3 eV. Through the
first and second steps, the work function of the carbon nanotubes
approximates that of silver nanowire.
[0038] In an embodiment of the present invention, the single-walled
carbon nanotubes having a functional group introduced thereto are
mixed and reacted with an isocyanate-based compound and a
pyrimidine-based compound, thereby reducing the work function of
the single-walled carbon nanotubes.
[0039] In the next third step, the work function-controlled
single-walled carbon nanotubes are dispersed in an
N-methylpyrrolidone solvent without the other additives, added in
different amounts to a solution of silver nanowires dispersed in
distilled water, and simply stirred, thus easily preparing a
coating solution in which the amount of the single-walled carbon
nanotubes is adjusted.
[0040] The prepared coating solution is applied on a polymer
substrate using a spray coater, yielding a transparent conductive
film.
[0041] Examples of the substrate may include glass, quartz, a
silicon wafer, plastics, etc.
[0042] The solution is applied on the substrate using any process
selected from the group consisting of spraying, dipping, spin
coating, screen printing, inkjet printing, pad printing, knife
coating, kiss coating, gravure coating, and slit coating.
[0043] FIGS. 2A-2D illustrate the SEM images of the surface of the
transparent conductive film for varying amounts of the
single-walled carbon nanotubes according to an embodiment of the
present invention.
[0044] FIG. 2A shows the case where carbon nanotubes are not
contained, FIG. 2B shows the case where the weight ratio of silver
nanowires and carbon nanotubes is 97:3, FIG. 2C shows the case
where the weight ratio of silver nanowires and carbon nanotubes is
93:7, and FIG. 2D shows the case where the weight ratio of silver
nanowires and carbon nanotubes is 80:20. As shown in FIGS. 2B to
2D, the silver nanowires and the carbon nanotubes are configured
such that a network is formed therebetween.
[0045] FIG. 3A to FIG. 3B illustrate changes in temperature when
voltage is applied to the silver nanowire transparent conductive
film of Comparative Example (FIG. 3A) and the silver
nanowire/carbon nanotube hybrid transparent conductive film of
Example according to the present invention (FIG. 3B), the
temperature distribution images being taken by an IR camera.
[0046] In FIG. 3, when the transparent conductive film was formed
of only the silver nanowires (FIG. 3A), hot spots were formed even
at a low voltage of 9 V, and thus the silver nanowires were melted.
However, the conductive film including the work function-controlled
carbon nanotubes was stably heated even when a voltage of 15 V or
more was applied, as is illustrated in FIG. 3B.
[0047] This can be also confirmed in FIG. 4. Based on the results
of SEM observation of the surface of the film after the application
of voltage, in the transparent conductive film (FIG. 4A) having no
work function-controlled single-walled carbon nanotubes, the
junctions of the silver nanowires were broken due to
high-temperature heating. However, as for the transparent
conductive film (FIG. 4B) of Example according to the present
invention, having work function-controlled single-walled carbon
nanotubes, a stable film was formed without damage to the silver
nanowires.
[0048] This is described with reference to FIG. 5. As illustrated
in FIG. 5A, when the carbon nanotubes are mixed and reacted with
the isocyanate-based compound and the pyrimidine-based compound in
this way, the work function of the carbon nanotubes is reduced, and
thus approximates the work function of the silver nanowires. As
illustrated in FIG. 5B, electricity is allowed to flow not toward
the junctions of the silver nanowires but toward the junctions
between the silver nanowires and the carbon nanotubes, whereby
local heating is minimized at the junctions and thus the electrical
stability of the silver nanowires is maintained.
[0049] As described above, in the manufacture of the transparent
conductive film having a network structure by hybridizing the work
function-controlled carbon nanomaterial with the metal nanowire,
the work function of the carbon nanomaterial is controlled so as
not to generate a significant difference from the work function of
the metal nanowire. Hence, when voltage is applied to the
transparent conductive film, current is induced to flow toward the
junction between the metal nanowire and the carbon nanomaterial,
rather than toward the junction of the metal nanowire, thus
assuring the electrical stability of the transparent conductive
film. As well, the use of the carbon nanomaterial having optically
low haze and mechanical stability results in a transparent
conductive film in which the haze of the metal nanowire network is
lowered and mechanical stability is enhanced.
[0050] The present invention pertains to a work function-controlled
carbon nanomaterial and metal nanowire hybrid transparent
conductive film and a method of manufacturing the same. More
particularly, the present invention can be useful in realizing a
work function-controlled carbon nanomaterial and metal nanowire
hybrid transparent conductive film, and is expected to be useful in
the manufacture fields thereof, wherein a conductive carbon
nanomaterial, such as carbon nanotubes, graphene, etc., is mixed
and reacted with an isocyanate-based compound and a
pyrimidine-based compound, thus forming a carbon nanomaterial, the
work function of which is controlled and which is dispersed without
the use of a dispersant, followed by hybridizing the carbon
nanomaterial with a metal nanowire having high conductivity, such
as a silver nanowire or a copper nanowire, to give a
single-component coating solution, which is then used to
manufacture a film configured such that a network is formed between
the metal nanowire and the carbon nanomaterial, thereby ensuring
electrical stability through work function matching of the metal
nanowire and solving optical problems such as haze.
* * * * *